The present invention relates to the field of video processing. More particularly, the present invention provides methods, apparatus, and systems for managing the insertion of overlay content into a video signal. In addition, certain example embodiments of the invention are directed towards insertion of overlay content into a video signal during transrating of the video signal.
Today's television images are frequently overlayed with additional content (referred to herein as “overlay content”), such as text messages, logos, animations, or sub-windows featuring full-motion video. Such edited signals are useful for conveying emergency information, targeted advertisements, or for customizing the message associated with a full-screen program or advertisement. There may be more than one candidate overlay content available for insertion into a particular video stream at a particular time. Although equipment for inserting or overlaying new content into full-screen video is readily available, such equipment is typically designed to operate with uncompressed video signals, and is purpose-driven for only those applications.
Encoded video signals based on compression standards such as MPEG present special challenges to the video editing process. A prior art system for inserting overlay content into a video signal is shown in FIG. 1. In the prior art, a decoder 10 fully decodes the video signals before the overlay content (auxiliary video) is inserted at a video editor 12. The modified video signal from the video editor 12 is then re-encoded at encoder 14 before being forwarded to the final destination. Not only is this solution expensive, but it can also degrade the quality of the video. For example, it is not uncommon to choose an expensive high-quality encoder for the original encoding process, and then economize on the cost of additional hardware if needed to process the signal in the smaller cable head-ends or other distribution sites serving a more limited audience.
Although it is possible to directly modify the video signal without using separate decoders, editors, and encoders, multiple problems need to be solved. For example, compression standards such as MPEG-2 and H.264 use motion compensation to predict the movement of features from one video frame to another. However, if one of these frames is altered by inserting or overlaying a different video image, then the synchronization between the decoder and the original encoder is destroyed. As a result, the motion prediction process will fail if a region of the image is encoded using a motion vector which crosses the boundary between the modified and unmodified regions of the image.
It would be advantageous to provide a simplified way to manage the insertion of overlay content into a video signal. In particular, it would be advantageous to enable overlay content to be closely correlated with a video signal into which the overlay content is to be inserted and/or with a video signal in a particular geographic region. It would also be advantageous to enable such close correlation between the overlay content and the video signal using tags with identifying information appended to the overlay content and/or the video signals. It would be further advantageous to enable the modification of compressed video signals with overlay content without the use of decoders and encoders. This results in considerable cost savings particularly when a large number of streams need to be processed. In addition, it would be advantageous to enable modification of the compression ratio of the video signal using the same insertion and overlay apparatus.
The methods, apparatus, and systems of the present invention provide the foregoing and other advantages. In particular, the present invention is particularly advantageous when combined with advanced transrating systems, such as the statistical multiplexers used in cable and other video distribution centers.